[pgpool-hackers: 2800] [New feature] Enable specifying SQL patterns lists that should not be load-balanced.

[Bo Peng]

Hi All

Here is a patch for new feature "Enable specifying 
SQL patterns lists that should not be load-balanced".

Even though currently we can do this by adding the 
/*NO LOAD BALANCE*/ comment to queries, this requires 
modifying application codes and this is not always 
possible.

This feature enables specifying SQL patterns lists 
that should not be load-balanced.

-------------
New parameter
-------------
black_query_pattern_list = ''

You can specify a semicolon separated list of SQL patterns 
that should be sent to primary node only. 

SQL that matched patterns specified in this list are not load balanced. 
Only Maste Slave mode is supported.

You can use regular expression to match SQL patterns, 
to which ^ and $ are automatically added. 
When using characters such as "'", ";" or "*" in SQL patterns, 
you need to escape them using "\". 


Example: 

If the following SQL should be sent to the primary node only,

    SELECT * FROM table_name1;

    SELECT * FROM table_name2 WHERE col LIKE '%a%';

    SQL including table_nama3 

You can set the black_query_pattern_list like below:

black_query_pattern_list = 'SELECT \* FROM table_name1\;;SELECT col1, col2 FROM table_name2 WHERE col1 LIKE \\'%a%\\'\;;.*table_name3.*'
          
-- 
Bo Peng <pengbo at sraoss.co.jp>
SRA OSS, Inc. Japan
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